Stepwise Mechanisms in the Ene Reaction of Alpha,Beta-Unsaturated Esters with N-Phenyl-1,2,4-Triazoline-3,5-Dione and Singlet Oxygen - Intermolecular Primary and Secondary Hydrogen Isotope Effects (EN)

Elemes, Y. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)

Elemes, Y. (EN)

Intermolecular primary and secondary isotope effects on the ene reaction of N-phenyl-1,2,4-triazoline-3,5-dione (PTAD) and singlet oxygen (O-1(2)) with deuterium-substituted (E)-2-methylbuten-2-oic (tiglic) acid methyl esters have been determined. In the case Of O-1(2), the primary isotope effect is 1.30-1.49 and the alpha and beta-secondary isotope effects are near unity, consistent with a stepwise reaction path via a perepoxide intermediate, where the allylic hydrogen-abstraction step is rate determining. On the other hand, the existence of both primary (1.44) and inverse alpha and beta-secondary isotope effects (0.91 and 0.77, respectively) in the PTAD reaction is consistent with either a concerted or a stepwise mechanism. Experiments in which both intermolecular primary and secondary isotope effects were measured at the same time suggest that, like singlet oxygen, PTAD reacts in a stepwise manner with the formation of the aziridinium imide intermediate (AI) in the rate-determining-step. (EN)

diels-alder reaction (EN)

Πανεπιστήμιο Ιωαννίνων

Ιδρυματικό Αποθετήριο Ολυμπιάς

Σχολή Θετικών Επιστημών

Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

ΑΠΟΘΕΤΗΡΙΟ "ΟΛΥΜΠΙΑΣ"

Τμήμα Χημείας

J Am Chem Soc (EN)

Αγγλική γλώσσα

1992

<Go to ISI>://A1992JE22500023

http://olympias.lib.uoi.gr/jspui/handle/123456789/9241

American Chemical Society (EN)